(Adapted from the applicant's abstract) The Gene Therapy/Molecular Biology Core will perform the following functions: 1) Develop new retroviral vectors for gene transfer; 2) Perform retroviral mediated gene transduction of hematopoietic cells; 3) Measure gene transfer in hematopoietic and lymphoid cells from laboratory and clinical studies; and 4) Perform FDA-mandated studies of patients who have received gene- modified cells.